1. Field of the Invention
The present invention relates to an apparatus and method for detecting a foreign material within a pouch type battery and, more particularly, to an apparatus and method for discriminating whether or not there is a foreign material within a battery by using a light scattering method on a surface of a battery case.
2. Description of the Related Art
In general, a pouch type battery is manufactured such that an electrode assembly, in which a positive electrode, a separator, and a negative electrode are alternately stacked, is mounted between laminate sheets, and the laminated sheets are thermally compressed.
In the process of manufacturing the pouch type battery, the positive electrode or the negative electrode may be notched or punched according to a desired size as necessary in order to manufacture the electrode assembly. The positive electrode and the negative electrode may have a solid active material layer, and the solid active material layer contains components such as an active material, an inorganic filler, and the like, and in the course of notching or punching operation, such components of the solid active material layer may be exposed as dust or mote.
The exposed dust or mote may fall back on an undesired portion of the electrode assembly or may be mounted as a foreign material or debris between the laminate sheet and the electrode assembly. The thusly mounted dust foreign material causes an undesired reaction in a charging or discharging process of the battery, greatly impairing the stability of the battery.
Thus, inspection of checking as to whether or not there is a foreign material in the battery must be necessarily performed before a final product is supplied to the market, and in general, one of the simplest methods of inspecting the presence or absence of a foreign material in the pouch type battery is observing the surface of the pouch during the operation by a worker.
The pouch type battery is manufactured by laminating the electrode assembly and the laminate sheet by heat, so if there is a foreign material between the electrode assembly and the laminate sheet, the surface of the laminated sheet, namely, the surface of the battery case, would be protruded correspondingly according to the shape of the foreign material. Thus, based on this, a foreign material within the battery can be inspected by simply checking the surface of the battery case.
As mentioned above, the related art method for inspecting the surface of the battery case is performed by the worker's naked eyes.
However, the related art method has a problem in that, because the worker directly inspects the battery case, the inspection speed is low. In particular, recently, the pouch type battery production process is performed by automated equipment and the manufactured batteries are rapidly transported by a transfer conveyer, so it is not possible for the worker to inspect the batteries at the rate of the rapidly transferred batteries. Thus, a method of sampling the batteries for inspection is employed; however, recently, as the stability of batteries is greatly issued, a total inspection is frequently performed to inspect every battery. Thus, a device for quickly inspecting the surfaces of battery cases is urgently required.
In addition, because the related art method relies on the naked eye inspection, dust foreign material in a micro size cannot be detected. In most cases, dust generated in the process of manufacturing batteries is too small to be recognized by the naked eyes. Thus, a device for accurately inspecting the surfaces of battery cases is urgently required.